Latest news from keithurban.net is that they're going to release the duet onto a compilation album.

Compilation album? When is it slated to be released?

Unless you've seen something I haven't, that was only posted by a fan who "heard it on the radio," not by anyone in any official capacity.

Jon did say on WGAR that he liked the idea of releasing it to benefit hurricane relief--if Keith's people would go for it. But he may have said that just to placate the interviewers.